Ventricular defibrillator



P. L. R. LOHR June 1l, 1963 VENTRICULAR DEFIBRILLATOR 5 Sheets-Sheet lFiled May 25, 1960 ../J m. ma Q @H w y y. o u B J J 0 W 2 6 f M Ca- 3- l.w 5 /CL P 1 2. 7 2 W M 2 i June 11, 1963 P. L. R. Lol-1R 3,093,136

VENTRICULAR DEFIBRILLATOR Filed may 25, 1960 s sheets-snaai 2 507 79//\/35/// 5]/ /Lv/ ///l v fag. 4 2

INVENTOR.

H 1 s AUTOR/VE V5 lune 11, 1963 Filed May 25. 1960 P. L. R. LOHRVENTRICULAR DEFIBRILLATOR 5 Sheets-Sheet 5 3,093,136 Patented June 1l,1963 [ice 3,093,136 VENTRICULAR DEFIBRILLATDR Paul L. R. Lohr,Baltimore, Md., assigner, by mesne assignments, to Mine SafetyAppliances Company, Pittsburgh, Pa., a corporation of Pennsylvania FiledMay 25, 1960, Ser. No. 31,776 14 Claims. (Cl. 12S- 423) This inventionrelates generally to a ventricular delibrillator for use in stoppingcardiac brillation by the rapid serial `discharge of a plurality ofcapacitators into a patients body in the region of the heart. Morespecifically, the invention relates to switch means for controlling thecharging and discharging operations of the defibrillator.

It is among the objects of this invention to provide switch means of thetype referred to Ithat will perform the following functions in theseque-nce stated: (1) In its normal position, the switch means connectthe capacitators in parallel to a charging circuit. (2) In its cockedposition, the switch means disconnect the capacitators from the chargingcircuit and connect them in series with a discharge circuit. (3) Inresponse to a predetermined pressure of both electrodes against thepatients body, and not otherwise, the switch means rapidly discharge thecapacitators serially into the patients body to arrest brillation. (4)After firing, the switch means return to their normal position toconnect the capacitators in parallel to the charging source inpreparation for a second shot if that should be necessary.

Further objects of the invention will be apparent from the followingdescription, in connection with the attached drawings, in which:

FIG. l is a schematic and wiring diagram of a defibrillatorincorporating the present invention;

FdG. 2 is a front elevation of a portion of the switch mechanism in itsnormal or uncocked position;

FIG. 3 is a plan View of the same switch mechanism in its cockedposition;

FIG. 4 is a front elevation of the switch mechanism on the line IV-IV ofFIG. 3;

FIG. 5 is an end elevation of the switch mechanism, gith a portionremoved for clarity, on the line V-V of FIG. 6 is a front elevation ofthe switch housing, partly in section, showing the switch cocking handleand the electrical contacts that are connected to the electrodes;

FIG. 7 is a sectional elevation of one of the electrodes mounted in itshandle; i

FIG, 8 is a plan View of the electrode in FIG. 6; and

FIG. 9 is a diagram showing the wave form of the electrical dischargethat lis applied to the patient.

In accordance with this invention, the switch means is used with acardiac defibrillator having a plurality of capacitators, a source ofelectrical energy for charging the capacitators, and a pair ofelectrodes adapted to be applied tothe patient. The switch meansincludes a movable spring-loaded switch arm (which controls otherspringloaded elements of the switch means)ladapted to move from a cockedposition to an uncocked position and, during its movement therebetween,to connect each of the capacitators successively and momentarily to theelectrodes. The switch also includes a latch for holding the movableswitch arm in its cocked position, this latch being releasable inresponse to a predetermined pressure of both electrodes against the bodyof the patient. More specically, the latch includes a spring-biasedlatch bar normally held in its latching position. Pivotally mounted onthe latch bar is a yoke, to the opposite ends of which are secured byflexible slack connectors the ends of two cables. The yoke is adapted tomove the latch bar to its releasing position when both cables arepulled.

If only one of the cables is pulled, the yoke merely turns on its pivotwithout displacing the latch bar. The other ends of the cables areattached to stems on the electrodes. The stems are received in hollowhandles, and pressure on those handles, with the electrodes placed onthe body of the patient, actuates the cables to release the latch bar.

Referring to the drawings, the general features of the defibrillator,including the electrical connections between its component parts, areschematically shown in FIG. 1. The broken line 1 outlines thosecomponents that are enclosed in a housing 2, as shown in other figures(FIGS. 246). A source of direct current (not shown) is connected toterminals 3 and 4, which represent, respectively, positive and negativeterminals. A multiple gang switch, represented generally by the numeral10, includes movable switch points 11, 12, 13 and 14 for opening andclosing switch contacts A, B, C, D, and E; it also includes a movableswitch arm 15 (which controls the positions of the switch points) and aswitch cocking lever I. The normal uncocked positions of the variousswitch elements are shown in solid lines in FIG. l, their cocked (orcocking, in the case of lever I) positions by broken lines. Themechanical structure and operation of the switch means are describedlater herein in connection with FIGS. 2-8.

In its normal uncocked position, switch means 10 connects capacitatorsC1 and C2 in parallel with the power terminals 3 and 4 to charge thecapacitators, as follows: Positive terminal 3 is connected throughconductor 5, closed switch contacts A and B, and conductor 16 to thepositive side of capacitator C1. Negative terminal 4 is connectedthrough conductor 6, closed switch contact E, and conductors 17 and 18to the negative side of that same capacitator. At the same time,capacitator C2 is connected to positive terminal 3 through conductor 5,closed switch contact A, and conductors 20 and 21, and to negativeterminal 4 through conductor 6, closed switch Contact E, conductors 17and 18, closed switch contact D, and conductor 22. A signal light 23 isconnected in series with a resistance 24 between conductors 21 and 22,and lights up when capacitator C2 is fully charged. Capacitators C1 andC2 have the same capacity; and, when one is fully charged, it is assumedthat the other will .also be fully charged.

In the normal uncocked position of the switch means, switch arm 15, andits cooking lever I occupy their solid line positions in FIG. l, so thatelectrode 30 is connected only to the negative terminal 4 of the powersource and to the negative sides of capacitators C1 and C2 whileelectrode 31 is not connected to either of the power termi nals or toeither of the capacitators. In the uncocked position of the switchmeans, the apparatus is therefore safe To cock the switch means, cockinglever I is manually turned in a clockwise direction to engage theunderside of switch arm 15 and turn the latter in the same directionuntil arm 15 is latched by a latch means L. Upon the cooking of arm 15,switch points 11--14 move to their broken line positions, opening switchcontacts A, B, D, and E .and closing switch contact C. Capacitators C1and C2 are now connected in series and, though disconnected from thepower terminals 3` and 4, are fully charged. Cookin-g lever I returns toits normal solid line position. Electrode 30 is connected to thenegative sides of capacitators C1 and C2, but electrode 31 is notconnected to either of the capacitators; and neither electrode isconnected to either of the power terminals. The cocked position is stillsafe When the swit-ch arm 15 is released or red, by the means describedbelow, it moves quickly from its broken line position under the urgingof its spring to its normal solid line position. As it does so, contactM on its outer end successively wipes contact points O and P todischarge capacitors C2 and C1 in that order through electrodes 30 and31 and the patients body (represented in FIG. l by the resistance R).The discharge circuit is as follows. As contact M on switch arm 15momentarily brushes contact O, current from the positive side ofcapacitator C2 flows through conductors 21 and 20, contacts O and M,switch arm 15, conductor 32, contact 33, conducting strip 34 on cockinglever I, contact 35, conductor 36, inductor 37, conductor 38 andelectrode 31 to the body of the patient R. At the same time, currentfrom the negative side of capacitor C2 flows through conductors 22 and39 to electrode 30, which is also in contact with the patients body R.The patient thereby receives a strong pulse 4of current having the waveform depicted in the first half of FIG. 9. This wave form shows thevoltage of the current pulse plotted against time, the portionof thewave above the horizontal line representing positive voltage and thatbelow the line representing negative voltage; alternating current pulseshaving this wave form have been found particularly suitable forarresting brillation of the heart.

As switch arm 15 continues to move from its cocked to its uncockedposition, its tip M momentarily brushes contact P, which dischargescondensers C1 into the body of the patient along the followingconducting paths. Current from the positive side of capacitator C1 flowsthrough conductor 16, closed switch contact C, and conductors 22 and 39to electrode 30. From the negative side of capacit-ator C1, currentflows through conductors 18 and 40, contacts P and M, switch arm 15,conductor 32, contact 33, conducting bar 34 on cocking lever J, contact35, conductor 36, inductor 37, and conductor 38 to electrode 31. Thepatient then receives a second pulse of current, owing in the reversedirection from that of the first pulse .and having the wave form shownin the second half of FIG. 9. These two pulses of current are generallysufficient to arrest fibrillation. Switch arm 15, after passing contactP and before returning to its initial position, causes movable switchpoints 11-14 to return to their normal solid line positions. Thecapacitators are then reconnected in parallel to the power terminals andare quickly recharged so that the process can be repeated, if necessary.

It should be noted that in cocking switch arm 15, its tip M brushes overcontacts P and O in a clockwise direction; but the capacitators cannotbe discharged, because cocking lever I has also moved clockwise from itsinitial position and opened a non-conducting gap between contacts 33 and35.

The physical structure of the switch means is shown in FIGS. 2-8.Referring iirst to FIGS. 2-6, the housing Z is provided with a compositeinsulated base 50 and 51, between the layers of which are concealed thepertinent wiring circuits shown in FIG. 1. Various mechanical componentsof switch means 10 are mounted on this base, including movable gangswitch arms '2 and 53 pivotally mounted in separate brackets 54 on pins55 and joined together by a striking bar 56. The switch arms 52 and 53are provided with switch heads 57 and 58, respectively. On the undersideof head 57 are mounted the movable switch points 11 and 12 adapted tomake and break connections with contacts A and B, respectively, mountedon base 50'. Switch head 58 has switch points 13V and 14 mounted on itsunderside adapted to make and break connections with contacts D and E,respectively, on the base 50. Switch point 13 is connected to asubsidiary switch point l13a (electrically, they are a single switchpoint, as represented in FIG. l, with a double throw action) on theupper surface of head 58. Switch point 13a is adapted to make and breakconnection with contact C mounted on the underside of a stop member 59,which is also secured to base 50. A similar stop member 60 (withoutcontacts) is provided for head 57. Accordingly, switch arms 52 yand 53are free to move in a limd. ited arc between contacts A, B, D and E onthe base 50 and contact C on stop member 59. Coil springs 62 (FIG. 3)urge these arms towards their elevated position (in which contact C isclosed, as shown in FIGS. 3 and 4). This corresponds to the cockedpositions of the switch points, as shown in broken lines in FIG. l.

Switch arms 52 and 53 are normally held, however, in their lower,uncooked positions, shown in FIG. 2, by switch arm 15. The latter isrotatably mounted on a shaft 63 supported in brackets 64 and urged by astrong spring 65 in a counter-clockwise direction against the strikerbar 56. Spring 65 is strong enough to overcome the combined opposingtorque of springs 52, so that switch arms 52 and 53 normally closecontacts A, B, D, and E, as shown by their solid line positions in FIG.1.

To cock the switch mechanism, knobI 70, which is mounted on the end ofshaft 63 projecting outside the housing, is turned manually in aclockwise direction to rotate cocking lever J, which is rigidly securedto shaft 63, against the urging of spring 71. Cocking lever J underliesswitch arm 15 and, on being turned in a clockwise direction, rotates`arm 15 about shaft 63 until `the arm is caught by the latchingmechanism L and held by the latter in its cocked position. Knob 70' isthen released and spring 71 returns the knob and cocking lever I totheir initial positions. During the cocking operation, when the strikerbar 56 is relieved of the pressure of switch arm 15, switch arms 52 and53 are urged by their springs 62 into the position shown in FIGS. 4 and5, in which contacts A, B, D, and E are open and Contact C is closed.

The latching mechanism L includes a latch bar 75, which 4is pivotallymounted on a pin 76 supported in a bracket 77 secured to the base 50. Acoil spring 78 urges the latch bar into its latching position, as shownin FIGS. 3 and 4, but not beyond that position due to the engagement ofthe forwardly projecting foot 79 of the latch bar against the stop 81 onthe base 50 (see FIG. 4).

The latch bar is provided with a beveled head 82, so that the latch barwill be displaced to the rear (FIGS. 2 and 3') when arm .15 is pushed`against the beveled surface by cocking lever I, to permit the arm topass below the latch head and to spring against its under side.Pivotally mounted on the latch bar is a yoke 90, which is adapted toturn in a substantially horizontal plane. To its ends 91 are secured byshort flexible connectors 92, the ends of two flexible wire cables 93.These cables are slidably received in flexible sheaths 94 that areclamped to the housing 2 by set screws 95. The other ends of thesheathed cables are connected to electrodes 301 and 31, as shown inFIGS. 7 and 8.

The two electrodes, generally identified by the numbers 30 and 31, areidentical in form and structure; and one of them is shown in FIGS. 7 and8. The electrode itself is a metal plate secured to the underside of aninsulating disc 101. The disc in turn is mounted concentrically on atubular stem 102, which is slidably received inside a hollow handle10-3. The latter is preferably lined with an anti-friction bearingsurface 104, such as a sleeve of Teflon.

The cable sheath 94 is secured to a guard disc 105 mounted on the lowerpart of the handle 103. The sheath extends, however, through a slot 106in the handle and an enlarged registering slot 107 in the stem. The endof cable 93 extends beyond its sheath and is anchored to the top of thestem by a plug 110, which is secured to the stem by a screw 111. Whenthe electrode assembly 30 or 31 is grasped by the handle and theelectrode plate 100 placed on the chest of the patient and the handlepressed downward, the stem is pushed into the handle against thepressure of a coil spring 112, its movement being limited to the initialspacing between the bottom of the handle 103 and disc 101. At the sametime, the end of the cable 93j, which is secured to the stem, is pulledaway from the adjacent end of the sheath which is attached to the guarddisc 105 to restrain i-t against axial movement, while the other end ofthe cable is moved in the opposite direction. The movement of the cableis suicient to take up the slack in the exible connector 92, connectingthe cable to the yoke 90, and to pull one end of the yoke towards therear of housing 2. If only one electrode is pressed against the patientsbody, the yoke will merely pivot, since there is sutiicient slack in theilexible connector 92 connecting the other cable and the yoke to permitlimited pivoting of the yoke. However, if both electrodes are pusheddown by pressure on their handles both cables will be activated bysubstantially the same amount and will pull the yoke Without appreciablerotation, causing the latching bar to pivot on its pin 76 to release orfire the switch arm 15. The electrical connection to the electrode plate100 is obtained by conductor 39 (or conductor 38) connected to the plateby a terminal screw 113.

During the tiring cycle after'switch arm 15 is released from thelatching bar, the arm turns rapidly on its shaft 63 in acounter-clockwise direction (see FIG. 4). Contact M on the outer end ofthis arm accordingly moves in an arc. Arm is of such length that contactM will clear the curved top portion 115 of housing Z, but will makesuccessive electrical contact with contact O and P secured to thiscurved portion of the housing (see FIG. 6). These contacts are made inrapid sequence and, as previously described, discharge the capacitatorsC2 and C1 in that order into the patients body. After the switch arm 15has passed contact P, it hits striker bar 56 forcing the gang switcharms 52 and 53 from their elevated positions shown in FIG. 4 to theirlowered positions shown in FIG. 2, thereby returning the switchmechanism to its initial, normal position.

It" desired, a second indicator circuit may be used to indicate thatcapacitator C1 is fully ch-arged and that the switch mechanism is in iscocked position. To that end, a signal light 120 (similar to signallight 23) is connected in series with a resistor 121 between thenegative termin-als of capacitators C1 and C2, as shown in FIG. l. Inthe uncocked position of the switch mechanism, the signal light is notenergized (cf.signal light 23, which is energized when capacitator C2 isfully charged with the switch mechanism in its uncocked position).However, when the switch mechanism is cocked and capacitator C1 is fullycharged, current will ow from the positive terminal of capacit-ator C1through conductor 16, closed contact C, conductor 22, signal light 120,and resistor 121 to the negative terminal of capacitator C-1.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated an-ddescribed.

I claim:

l. For use in a cardiac debrillator having a plurality of condensers anda source of electrical energy for charging the condensers and a pair ofelectrodes adapted to be applied to the body of a patient, switch meansfor serially discharging the condensers through the electrodes and thepatients body, said switch means comprising: a movable electricalcontact adapted to move from a cocked position to an uncocked position,a plurality of xed electrical contacts disposed in the path of movementof the movable contact and adapted to be successively and momentarilyengaged by the movable contact when moving from its cocked to itsuncocked position, each of the fixed contacts when so engaged connectingthrough the movable contact a yseparate condenser across the electrodes,means for rapidly moving the movable contact from its cocked to itsuncocked position, a releasa-ble latch for holding the movable contactin its cocked position, and means for releasing the latch that areoperative solely in response to a predetermined pressure of bothelectrodes against the body of the patient.

2. Apparatus according to claim l, in which the means for releasing thelatch include a yoke pivotally mounted on the latch for moving the latchinto its releasing position when the pivotal axis of the yoke isdisplaced a predetermined amount in a given direction, and means mountedon each electrode and connected to the ends of the yoke for displacingthe pivotal axis of the yoke only when both electrodes are pressedagainst the patients body.

3. Apparatus according to claim 1, in which the means for releasing thelatch include a yoke pivotally mounted on the latch for moving the latchinto its releasing position when the pivotal axis of the yoke isdisplaced a p-redetermined amount in a given direction, actuating meansmounted on each electrode and movable in response to pressure of theelectrode against the patients body, separate connecting means extendingbetween each electrode and the yoke, the yoke ends of the connectingmeans being attached to the yoke at points on opposite sides of itspivotal axis and substantially equally spaced therefrom and theelectrode ends of the connecting means being attached to the actuatingmeans on the electrodes', whereby when both electrodes are pressedagainst the patients body and the actuating means are displaced bysubstantially equal amounts the pivotal axis of the yoke will bedisplaced by substantially the same amount to move the latch to itsreleasing position.

4. Apparatus according to claim 3, in which the actuating means includea stem mounted on each electrode and connected to the electrode end ofone of the connecting means, a hollow handle with one end closed and theother end slidably receiving the stem, and a coil spring between theclosed end of the handle and the stem.

5. Apparatus according to claim 3, in which the connecting means is ailexible wire slidably received in a iiexible sheath, and means forsecuring the sheath against axial movement.

6. Apparatus according to claim 3, in which each connecting meansincludes a ilexible wire slidably received in a exible sheath that issecured against axial movement and a normally slack ilexible memberconnecting the yoke end of the wire with the yoke.

7. For use in a cardiac delibrillator having a plurality of condensers,a source of electrical energy for charging the condensers, and a pair ofelectrodes adapted to be applied to the body of a patient, switch meansfor charging the condenser and for serially discharging them through theelectrodes and the patients body, said switch means comprising: a gangswitch having a rst operative position in which it connects thecondensers in parallel to the source of electrical energy for chargingthe condensers and a second operative position in which it disconnectsthe condensers from said source, iirst spring means urging the gangswitch into its second operative position, a switch arm adapted tooccupy cocked and uncocked positions, second spring means urging theswitch arm into its uncocked position in which the switch arm engagesthe gang switch and holds it in its first operative position against theurging of the rst spring means, means for cocking the switch arm therebyreleasing the gang switch and allowing the latter to assume its secondoperative position, a latch -for holding the switch arm in its cockedposition, means for releasing the latch solely in response to apredetermined pressure on both electrodes, a plurality of fixed spacedcontacts adapted to be successively and momentarily engaged by theswitch arm when the latter moves 4between its cocked and its uncockedpositions, the switch arm when released from its cocked positionreturning rapidly to its uncocked position and during such returnmovement successively and momentarily connecting the condensers throughthe iixed contacts across the electrodes and 7 finally engaging the gangswitch and moving it from its second to its first operative position.

8. Apparatus in accordance with claim 7, in which the means for cookingthe switch arm includes a manually rotatable cocking lever adapted whenrotated to engage the switch arm and rotate it from its uncocked to itscocked position, and spring means for returning the cocking lever to itsinitial position.

9. Apparatus according to claim 8, in which the cocking lever when movedfrom its initial position opens said electrical circuit between thecondensers and the electrodes.

10. Apparatus according to claim 7, in which the latch means includes aspring-biased latching bar normally held in its latching position, vayoke pivotally mounted on the latching bar for moving the bar into itsreleasing position when opposite .ends of the yoke are displaced `apredetermined amount in the same direction, and means actuated bypressure on both electrodes for `displacing the yoke.

11. Apparatus according to claim 7 that also includes indicating meansoperative when one of the condensers is fully charged and the switch armis in its uncocked position.

12. Apparatus according to claim 7 that also includes indicating meansoperative when one of the condensers is fully charged and the switch`arm is in its cocked position.

13. Apparatus according to claim 7, in which the means for releasing thelatch includes a yoke pivotally mounted on the latch and adapted to movethe latch into its releasing position when opposite ends of the yoke aredisplaced a predetermined amount in the same direction, a stern mountedon each electrode, a hollow handle with one end closed and the other endslidably receiving the stem, a coil spring between the closed end of thehandle and the received end of the stern, and ilexible means connectingeach stem with a different end of the yoke, whereby pressure exerted onthe handles of both electrodes urging the electrodes against the body ofthe patient will cause the flexible means to displace the yoke anddisengage the latch from the switch arm.

14. Apparatus according to claim 7, in which the gang switch in itssecond position connects the positive side of a rst charged condenserand the negative side of a second charged condenser to the sameelectrode, so that one condenser will discharge a pulse of current inone direction across the electrodes and the other condenser willdischarge a pulse in the opposite direction.

References Cited in the le of this patent UNITED STATES PATENTS 938,399Schauer Oct. 26, 1909 1,352,889 Gallo Sept. 14, 1920 1,733,763 WernerOct. 29, 1929 1,851,504 Florsheim Mar. ,29, 1932 2,452,854 Joy Nov. 2,1948 2,764,683 Paust Sept. 25, 1956 OTHER REFERENCES Factors Concernedin Electrical Debrillation by A. C. Guyton, in American Journals ofPhysiology, Oct. l, 1951, pp. 81-87.

1. FOR USE IN A CARDIAC DEFIBRILLATOR HAVING A PLURALITY OF CONDENSERSAND A SOURCE OF ELECTRICAL ENERGY FOR CHARGING THE CONDENSERS AND A PAIROF ELECTRODES ADAPTED TO BE APPLIED TO THE BODY OF A PATIENT, SWITCHMEANS FOR SERIALLY DISCHARGING THE CONDENSERS THROUGH THE ELECTRODES ANDTHE PATIENT''S BODY, SAID SWITCH MEANS COMPRISING: A MOVABLE ELECTRICALCONTACT ADAPTED TO MOVE FROM A COCKED POSITION TO AN UNCOCKED POSITION,A PLURALITY OF FIXED ELECTRICAL CONTACTS DISPOSED IN THE PATH OFMOVEMENT TO THE MOVABLE CONTACT AND ADAPTED TO BE SUCCESSIVELY ANDMOMENTARILY ENGAGED BY THE MOVABLE CONTACT WHEN MOVING FROM ITS COCKEDTO ITS UNCOCKED POSITION, EACH OF THE FIXED CONTACTS WHEN SO ENGAGEDCONNECTING THROUGH THE MOVABLE CONTACT A SEPARATE CONDENSER ACROSS THEELECTRODES, MEANS FOR RAPIDLY MOVING THE MOVABLE CONTACT FROM ITS COCKEDTO ITS UNCOCKED POSITION, A RELEASABLE LATCH FOR HOLDING THE MOVABLECONTACT IN ITS COCKED POSITION, AND MEANS FOR RELEASING THE LATCH THATARE OPERATIVE SOLELY IN RESPONSE TO A PREDETERMINED PRESSURE OF BOTHELECTRODES AGAINST THE BODY OF THE PATIENT.